Protein adducts in type I and type II fibre predominant muscles of the ethanol-fed rat: preferential localisation in the sarcolemmal and subsarcolemmal region

Background Chronic alcoholic myopathy is characterised by reduced muscle st rength and structural changes including a decrease in the diameter of Type II (glycolytic, fast-twitch, anaerobic) fibres. In contrast, the Type I fib res (oxidative, slow-twitch, aerobic) are relatively protected. It is possi ble that adduct formation with reactive metabolites of ethanol may be a con tributory process. Materials and Methods We analysed skeletal muscles from rats fed nutritiona l-complete liquid diets containing ethanol as 35% of total dietary energy; control rats were fed the same diet in which ethanol was replaced by isocal oric glucose. Reduced-acetaldehyde, unreduced-acetaldehyde, malondialdehyde , malondialdehyde-acetaldehyde and alpha -hydroxyethyl protein-adducts in b oth soleus and plantaris were analysed by ELISA or immunohistochemistry wit h comparative studies in liver. Results After 6 weeks, the weights of the plantaris, but not the soleus, we re decreased. ELISA analyses for protein adducts showed increased amounts o f unreduced-acetaldehyde adducts in soleus (P < 0.025) and plantaris (P < 0 .025). Reduced-acetaldehyde, malondialdehyde, malondialdehyde-acetaldehyde and alpha -hydroxyethyl protein-adducts in both soleus and plantaris muscle s from ethanol-fed rats were not significantly different from their pair-fe d controls (P > 0.05). In contrast, liver from ethanol-fed rats showed sign ificantly higher levels of unreduced-acetaldehyde (P < 0.025), reduced-acet aldehyde (P < 0.01), malondialdehyde (P < 0.01), malondialdehyde-acetaldehy de (P < 0.025) and a-hydroxyethyl radical (P < 0.01) protein adducts compar ed to pair-fed controls. Immuno-histochemical analysis using an antiserum r eacting with both reduced- and unreduced-acetaldehyde adducts showed adduct s were increased in soleus (P < 0.05) and plantaris (P < 0.025), confirming ELISA analysis. Adducts were located within the sarcolemmal (i.e. muscle m embrane) and subsarcolemmal regions. Conclusion This is the first report of adduct formation in myopathic skelet al muscle due to chronic alcohol ingestion and suggests a role for acetalde hyde in the aetiology of alcoholic myopathy.